1. Field of the Invention
This invention is directed to tension clamping devices for screens mounted on vibratory screening system; to systems with such devices; and to methods of their use.
2. Description of Related Art
The prior art discloses a variety of devices and apparatuses for securing a screen to a vibratory screening apparatus. Many of the prior art systems employ a simple bolt, nut, and plate combination, with or without shock absorbing material. Tightening and loosening of the nut provides tension adjustment. Exemplary prior art patents include, but are not limited to, U.S. Pat. Nos. 4,303,509; 5,332,101; and 5,392,925.
U.S. Pat. No. 5,332,101 discloses a screen tensioning structure that includes body members with a cam arrangement whose movement creates a pulling effect when cam followers slide up camtracks. Certain commercially available embodiments require a special wrench to turn a movable adjustment nut. Often, the nut can only be effectively adjusted when the structure is in an unlocked position. With some prior art devices sliding surfaces must be lubricated regularly, otherwise the surfaces gall making high torque necessary, which in turn requires a high wrench load which can result in a bent tension bolt.
Certain prior art devices can result in insufficient tension on a screen when their springs collapse (take a set) reducing the total tension load produced by the spring. Many times the only way to then achieve proper tension on a screen is to collapse the spring completely and torque the spring adjusting nut.
There has long been a need for an efficient and effective screen tensioning clamp apparatus. There has long been a need for such an apparatus that can be used with existing vibratory system screen mounts without requiring changes and alternations to the vibratory system. There has long been a need for such an apparatus which is adjustable while in a locked position. There has long been a need for such an apparatus that reduces misalignment between the apparatus and structural members of the vibratory system.